Wednesday, August 8, 2007: 10:10 AM
N, San Jose McEnery Convention Center
Earthworms are among the most important detritivore animals in terrestrial ecosystems and function as ecosystem engineers. Especially in grasslands they are known to play a key role in nutrient cycling, physical soil improvement, and therefore in plant growth. A recent study showed that the effect of earthworms is more pronounced in grasses than in legumes suggesting that earthworm effects vary with plant functional groups. However, population oscillations of grasses and legumes are poorly understood.
In a greenhouse experiment we investigated the impact of earthworms (Lumbricus terrestris) on performance of and competition between grasses and legumes using common plant species of “The Jena Experiment”. Therefore, we set up 90 mesocosms containing twelve plant individuals. In half of the pots two individuals of Lumbricus terrestris were added. Plant performance parameters and aphid infestation rates were recorded after 6 and 16 weeks.
The presence of L. terrestris increased the productivity of grasses and legumes after 6 weeks but only that of grasses after another 10 weeks. Both the presence of grasses and the presence of L. terrestris decreased the number of legume flower heads. Also, the presence of L. terrestris and the presence of legumes increased the infestation of grasses with aphids. The results indicate that grasses are stronger competitors for soil resources than legumes. Presumably, compared to legumes grasses more efficiently exploit mineral nitrogen mobilized by earthworms and also benefit from nitrogen fixation by legumes. Data on infestation of grasses with aphids support our hypothesis.
In a greenhouse experiment we investigated the impact of earthworms (Lumbricus terrestris) on performance of and competition between grasses and legumes using common plant species of “The Jena Experiment”. Therefore, we set up 90 mesocosms containing twelve plant individuals. In half of the pots two individuals of Lumbricus terrestris were added. Plant performance parameters and aphid infestation rates were recorded after 6 and 16 weeks.
The presence of L. terrestris increased the productivity of grasses and legumes after 6 weeks but only that of grasses after another 10 weeks. Both the presence of grasses and the presence of L. terrestris decreased the number of legume flower heads. Also, the presence of L. terrestris and the presence of legumes increased the infestation of grasses with aphids. The results indicate that grasses are stronger competitors for soil resources than legumes. Presumably, compared to legumes grasses more efficiently exploit mineral nitrogen mobilized by earthworms and also benefit from nitrogen fixation by legumes. Data on infestation of grasses with aphids support our hypothesis.
